Shown for comparison with a full sized Rolex Submariner you can see how thick the case of the DS-2 is.

This is a very thoughtfully designed watch. The 5mm thick acrylic crystal is sealed against the case with an o-ring, and secured by a threaded retaining ring. The retaining ring is easily removed, allowing easy replacement and servicing of the crystal, o-ring and bezel without the need of a watchmaker or watchmaker's tools. The bezel on this watch has one of the most precise actions I have seen on any watch, vintage or modern. Drilled case lugs are a nice touch and make strap changes fast and easy.

Today Certina is just another brand name in the SWATCH GROUP, but back in the day Certina built their reputation with some very serious dive hardware.